Flutter, a phenomenon where flexible structures are subjected to aerodynamic forces, can affect airplanes, buildings, bridges, power lines, and more. A notable example of how aerodynamics can impact a structure is the famous 1940 collapse of the Tacoma Narrows Bridge, where high winds shifted the bridge deck in alternating twisting motions, resulting in it being torn apart. Beyond buildings and bridges, aircraft are also vulnerable to aerodynamics. Today, aircraft (and structures) go through ground vibration testing to predict their behavior under different physical conditions. Engineers use experimental modal parameters to analyze the structural dynamics model, which is critical for tuning joints and connections, but not an exact process. Often only partial correlation is possible, and discrepancies between analysis results and experimental data can be challenging to explain.
Researchers Giuseppe Maurizio Gagliardi, Mandar D. Kulkarni, and Francesco Marulo sought to minimize the differences between numerical results and experimental measurements to achieve an efficient flutter prediction. In their study, “Aerodynamic Flutter Analysis Based on Experimental and Hybrid Modal Parameters,” the authors offer a reliable aeroelastic model. By combining ground vibration testing data (to perform aeroelastic simulations) and experimental modal parameters (to develop hybrid aeroelastic models) this new model could improve the reliability of flutter prediction. To conclude their study, the authors successfully applied their model to a practical case. Learn more about this research in the Journal of Aerospace Engineering at https://doi.org/10.1061/JAEEEZ.ASENG-5533. The abstract is below.
Abstract
The use of experimental data is a relevant topic in aeroelasticity. A new aircraft prototype design and certification involve both flutter analysis and tests. The latter is essential to assess a proper finite element (FE) model for the aeroelastic analysis. The current work perfectly fits in this framework, presenting a novel methodology exploiting data from ground vibration testing (GVT) for flutter calculations. The first application relies on the only experimental modal parameters employed to perform aerodynamic flutter calculation. This method does not necessitate a consistent structural model, allowing fast and reliable computation of the flutter clearance just based on GVT results. This application is especially valuable when it is not possible for a structural dynamic model development, e.g., in the absence of a sufficient amount of technical data. The method also allows combinations of experimental and numerical mode shapes to perform flutter calculations. All or some modal parameters can be incorporated in the standard numerical flutter model, adjusting the computed numerical modes, or adding/deleting a few. The method allows a real true correlation between the GVT results and the numerical model, which is usually very difficult to obtain. This work represents the first case based on a combination of experimental and numerical results, paving the way to various possible levels of hybridization to perform aeroelastic analyses.
Learn more about how this new model could improve the reliability of flutter prediction in the ASCE Library: https://doi.org/10.1061/JAEEEZ.ASENG-5533.
